Geochemical Characteristics And Tectonic Significance Of Yemaquan Granodiorite In Ejina Banner,Inner Mongolia

The Yemaquan area in Ejina Banner of Inner Mongolia is located in the eastern part of beishan orogenic belt.Affected by the fault activities of the Hongqiquan-Yemaquan near the EW direction,there are complex geological structures and various types of intrusions.Due to its special geographical location,the genesis and tectonic setting of granites have always been the subject of geologists.There are a large number of granodiorites in The Yemaquan area,but the research on this kind of granites is relatively limited at present.Therefore,the research on geochronology and geochemistry is helpful to better clarify the genesis and tectonic setting of granites in this area.For this reason,this paper selects the Yemaquan granodiorite in Ejina Banner,Inner Mongolia,as the research object.Through field geological survey,petrology,petrography,LA-ICP-MS zircon U-Pb chronology,whole rock geochemistry,zircon Lu-Hf isotope and whole rock Sr-Nd isotope,etc.The formation age of the granodiorite is determined,the genetic mechanism of the granodiorite is discussed.And the tectonic environment of the Beishan area in the Early Devonian is discussed based on the geological evidences of the previous granite data and stratigraphy,structure and sedimentary environment.On the one hand,it can not only provides detailed basic data for the study of Paleozoic tectonic pattern and formation history of Beishan orogenic belt.On the other hang,it can also provides corresponding evidence for the study of tectonic evolution of Central Asian orogenic belt and the growth of continental crust.The Yemaquan granodiorite was formed in the Early Devonian(419.4±3.3Ma and 418.5±1.8Ma),high silicon(66.05%on average),high potassium(2.77%on average),low in magnesium(1.73%on average)and Characteristics of aluminum(14.23%on average).It belongs to high potassium calc alkaline-calc-alkaline,Metaluminous-weak peraluminous series.These granodiorites are a set of undifferentiated type I rocks,which are enriched in large ion lithophile elements such as Rb,Th,U,K and deficient in high field strength elements such as Ta,Nb,Ti,P.Zircon?Hf(t)has a wide range of variation(positive or negative),and the average age of TDM2 is 1.34Ga and 1.44Ga,which is consistent with that of Sr-Nd isotopes(1357?1487Ma).Combined with the characteristics of high(⁸⁷Sr/⁸⁶Sr)i And low?Nd(t)of the Granodiorite,It is suggested that the magma source of the Yanmaquan granodiorite is a crust,involving at least two sources of the old crust and the juvenile crust.According to this article and predecessors'achievements,it is believed that Yemaquan granodiorite may be early devonian oceanic crust subduction cut stage of the product,the period may be important ocean-continent subduction-collision of beishan area tectonic transformation period.